Apparatus and method of use for treating blood vessels

ABSTRACT

An electrosurgical apparatus is provided. The electrosurgical apparatus includes a cannula insertable into a patient and positionable adjacent abnormal tissue. The electrosurgical apparatus includes a microwave antenna that includes a distal end having a radiating section receivable within the cannula and positionable within a patient adjacent abnormal tissue. The microwave antenna is adapted to connect to a source of electrosurgical energy for transmitting electrosurgical energy to the radiating section. A portion of the radiating section substantially encompasses a portion of the abnormal tissue and may be configured to apply pressure thereto. The microwave antenna is actuated to electrocautery treat tissue to reduce blood flow to the abnormal tissue.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patent application Ser. No. 12/696,671, filed on Jan. 29, 2010, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an apparatus and method for treating blood vessels. More particularly, the present disclosure relates to an apparatus including a microwave antenna having a radiating loop configuration that is utilized for treating blood vessels.

2. Background of Related Art

In recent years a number of non-invasive techniques have been developed to repair abnormalities (e.g., aneurysms, arterio-venous fistulas, varicose veins, etc.) occurring in hollow body biological organs and/or vessels. Typically, the non-invasive techniques generally seek to “re-line” the blood flow path through the organ and/or vessel.

For example, in the instance of a vessel afflicted with an aneurysm, endovascular techniques typically involve attempting to form a mass within a sac of the aneurysm. Typically, a microcatheter (or other suitable device) is used to access the aneurysm. More particularly, a distal tip of the microcatheter is placed within a blood vessel (e.g., a parent artery or vein) that is in fluid communication with the sac of the aneurysm. Thereafter, the distal tip of the microcatheter is used to inject embolic material into the sac of the aneurysm. In certain instances, the embolic material may include, for example, detachable coils or an embolic agent.

Disadvantages associated with injecting embolic material into the sac of the aneurysm include migration of the embolic material out of the sac of the aneurysm and into the parent artery afflicted with the aneurysm. Migration of the embolic material can cause permanent and irreversible occlusion of the parent artery. For example, when detachable coils are used to treat, e.g., occlude, an aneurysm, the detachable coils may migrate out of the sac of the aneurysm and into the patient's artery. Moreover, it is, at times, difficult to gauge the exact size of the sac of the aneurysm when the detachable coils are being injected into the sac. Therefore, there is a risk of overfilling the sac of the aneurysm in which case the detachable coils may spill out of the sac of the aneurysm and into the patient's artery, which may result in permanent and irreversible occlusion of the patient's artery. Another disadvantage associated with the use of detachable coils in treating an aneurysm involves coil compaction over time. More particularly, after filling a sac of the aneurysm with detachable coils, space may remain between the detachable coils. Continued hemodynamic forces from blood circulation act to compact the detachable coil mass, which, in turn, may result in a cavity in the aneurysm neck. As a result thereof, the aneurysm may recanalize which, in turn, may lead to blood flowing through the neck of the aneurysm and into the sac of the aneurysm. Embolic agent (e.g., a liquid polymer) migration is also a problem. More particularly, when a liquid polymer is injected into the sac of the aneurysm, it (the liquid polymer) can migrate out of the sac of the aneurysm due to the hemodynamics of the system; this can also lead to irreversible occlusion of the parent vessel.

Another endovascular technique for treating aneurysms involves inserting a detachable balloon (or other suitable device) into a sac of the aneurysm using a microcatheter. In this instance, the detachable balloon is inflated using embolic material, such as liquid polymer material. The balloon is then detached from the microcatheter and left within the sac of the aneurysm in an attempt to fill the sac of the aneurysm and form a thrombotic mass in the aneurysm. However, detachable balloons also suffer disadvantages. For example, detachable balloons, when inflated, typically do not conform to the interior configuration of the aneurysm sac. Instead, the detachable balloon requires the sac of the aneurysm to conform to the exterior surface of the detachable balloon. Thus, there is an increased risk that the detachable balloon will rupture the sac of the aneurysm.

As an alternative to the foregoing endovascular techniques, or in combination therewith, a distal tip of a microwave antenna may be placed within a blood vessel (e.g., an artery or vein) that is in fluid communication with the sac of the aneurysm. In this instance, the microwave antenna and/or distal tip is configured to treat the aneurysm via electrosurgical energy (e.g., RF or microwave energy). More particularly, the distal tip is configured to heat the interior of the sac aneurysm, i.e., heat the blood within the aneurysm, until a thrombus or thrombotic mass is formed.

SUMMARY

The present disclosure provides an electrosurgical apparatus. The electrosurgical apparatus includes a cannula insertable into a patient and positionable adjacent abnormal tissue. The electrosurgical apparatus includes a microwave antenna that includes a distal end having a radiating section receivable within the cannula and positionable within a patient adjacent abnormal tissue. The microwave antenna is adapted to connect to a source of electrosurgical energy for transmitting electrosurgical energy to the radiating section. A portion of the radiating section substantially encompasses a portion of the abnormal tissue and may be configured to apply pressure thereto. The microwave antenna is actuated to electrocautery treat tissue to reduce blood flow to the abnormal tissue.

The present disclosure provides a method for treating various abnormalities associates with blood vessels. The method includes an initial step of positioning a cannula adjacent an abnormal tissue. Inserting a microwave antenna including a radiating section defining a radiating loop into the cannula is a step of the method. In some embodiments, the microwave antenna is adapted to connect to a source of electrosurgical energy for transmitting electrosurgical energy to a portion of the radiating section. A step of the method includes positioning the radiating loop adjacent the abnormal tissue such that the radiating loop applies pressure thereto. Transmitting electrosurgical energy to the radiating loop to treat tissue is another step of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a microwave ablation apparatus adapted for use with a microwave antenna that utilizes a deployable loop configuration for treating blood vessels according to an embodiment of the present disclosure;

FIGS. 2A-2E are schematic views illustrating a method of use for the microwave apparatus depicted in FIG. 1 in accordance with an embodiment of the present disclosure;

FIGS. 3A-3D are schematic views illustrating a method of use for the microwave apparatus depicted in FIG. 1 in accordance with an alternate embodiment of the present disclosure;

FIGS. 4A-4D are schematic views illustrating a method of use for the microwave apparatus depicted in FIG. 1 in accordance with another embodiment of the present disclosure;

FIGS. 5A-5C are schematic views illustrating a method of use for the microwave apparatus depicted in FIG. 1 in accordance with yet another embodiment of the present disclosure; and

FIG. 6 is a flowchart illustrating a method for treating various blood vessel abnormalities.

DETAILED DESCRIPTION

Embodiments of the presently disclosed apparatus and methods are described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. As used herein and as is traditional, the term “distal” refers to the portion which is furthest from the user and the term “proximal” refers to the portion that is closest to the user. In addition, terms such as “above”, “below”, “forward”, “rearward”, etc. refer to the orientation of the figures or the direction of components and are simply used for convenience of description.

Referring initially to FIG. 1, a microwave ablation apparatus according to an embodiment of the present disclosure is shown designated 10. As shown, microwave ablation apparatus 10 includes an electrosurgical energy source 20 (e.g., a generator 20 configured to produce RF or microwave electrosurgical energy) that is adapted to connect to a catheter or cannula 30 including a microwave antenna 50 that utilizes a deployable loop configuration for treating blood vessels. Cannula 30 includes a proximal section 32, a distal section 34 including a tip section 36.

Cannula 30 may have any suitable dimensions (e.g., width, height, length, thickness etc.). More particularly, a length of the cannula 30 is typically such that cannula 30 may be readily manipulated by a user and inserted into a body of a patient, either percutaneously, endoluminally, or during an open procedure. By way of example only, the thickness, e.g., diameter, of cannula 30 may also vary depending upon factors that include, but are not limited to, the materials from which cannula 30 is formed, the thickness of microwave antenna 50, the type of procedure, etc.

Proximal section 32 may be formed from any suitable material. More particularly, proximal section 30 may be formed from materials including, but not limited to, medical grade polyolefins, fluoropolymers, polyurethane, or polyvinylidene fluoride. In certain instances, proximal section 32 may be stiffened using stainless steel braided wires, or similar structures, that are arranged to allow proximal section 32 to sustain torque. As is conventional in the art, proximal section 32 may have a relatively high durometer such that proximal section 32 is considered to be relatively “stiff.”

A handle 38 is coupled to proximal section 32 in order to enable cannula 30 to be gripped by a user. It should be appreciated, though, that in some embodiments, a handle such as handle 38 that is coupled to proximal section 32 is not necessarily provided. Suitable catheters may also be utilized. In proximity to handle 38 is a connector 40 that is arranged to couple a transmission line (not shown) associated with cannula 30 to a generator 20 (or similar device) that is designed to generate controlled electrosurgical energy, e.g., microwave energy.

Distal end 34 may be operably coupled to the proximal end 32 by any suitable method(s) and/or structure(s). In the illustrated embodiment, distal end 34 (including distal tip 36) is monolithically formed with the proximal end 32. Distal tip 36 may be a relatively sharp to penetrate tissue, e.g., skin, and may include a generally arcuate or curved shape to facilitate positioning of the microwave antenna 50 or portion associated therewith adjacent tissue.

In one embodiment, microwave antenna 50 is configured to be inserted percutaneously into a patient and deployed adjacent a target tissue site, e.g., a target abnormality associated with a blood vessel. With this purpose in mind, microwave antenna 50 is positionable within the cannula 30 and extends along the length of the cannula 30. More particularly, a proximal end 51 of the microwave antenna 50 operably couples to the generator 20 via one or more internal components associated with the handle 38 and/or connector 40. Microwave antenna 50 is movable within the cannula 30 from a non-deployed position (not explicitly shown) to a deployed position (FIG. 1). Microwave antenna 50 may be made from any suitable material, including but not limited to stainless steel, tungsten, copper, etc. In one particular embodiment, a proximal portion 51 of the microwave antenna 50 is a conductive wire or cable made from tungsten. The proximal portion 51 of the microwave antenna 50 may be coated with one or more dielectric materials. In addition, proximal portion 51 may have any suitable shape.

More particularly, a cross-section of the proximal portion 51 may have a circular shape, a half-circular shape, an oval shape, a flat shape, etc. Proximal portion 51 may have any suitable dimensions. In the illustrated embodiment, proximal portion 51 includes a cross-sectional diameter that ranges from about 0.0010 inches to about 0.020 inches. A portion of the microwave antenna 50 is configured to transmit microwave energy to a target tissue site (e.g., a target abnormality associated with a blood vessel). More particularly, a distal end 52 of the microwave antenna 50 is configured to wrap around and contact or squeeze an abnormality associated with a blood vessel. To this end, the distal end 52 is operably coupled to (by any suitable method(s)) and in electrical communication with the proximal end 51 of the microwave antenna 50 and includes a radiating section 54 having a loop configuration (“loop” 56) with a loop diameter of suitable proportion.

In the illustrated embodiment of FIG. 1, radiating section 54 is made from a suitable shape memory alloy, such as, for example, Nitinol (other shape memory alloys may be utilized and are contemplated). As is known in the art, shape memory alloys transition from an initial state to an original or “cold forged” state. In accordance with the present disclosure, radiating section 54 may have any suitable configuration when in an initial state, i.e., a state other than the “cold forged” or “looped” state. More particularly, in an embodiment, the radiating section 54 includes a generally straight or linear configuration (see FIG. 1). Alternatively, the radiating section 54 may be pre-formed (by any suitable method(s)) with a loop 56, shown for illustrative purposes in FIG. 1 unassembled from microwave antenna 50. In this instance, the radiating section 54 may be made from any suitable material including those described above with respect to proximal end 51. Radiating section 54 includes a “cold forged” state having a loop diameter of suitable proportion.

More particularly, a suitable loop diameter is one that is sufficient to fully wrap around or substantially encompass a target abnormality and may be configured to apply a closing or squeezing pressure of suitable proportion to the target abnormality. In one particular embodiment, the loop diameter ranges from about 10 mm to about 20 mm. The combination of wrapping around and squeezing the target abnormality facilitates in providing a desired tissue effect to the target abnormality. For example, wrapping around the target abnormality while applying a predetermined pressure thereto provides a consistent and uniform treatment to the target abnormality.

In accordance with the present disclosure, when electrosurgical energy, e.g., microwave energy, is transmitted to the microwave antenna 50 and, more particularly, to the radiating section 54, the radiating section 54 transitions from its initial state, i.e., its “non-looped” state (FIG. 1) to its original or “looped” state (shown in phantom in FIG. 1). In the looped state, loop 56 wraps around and closes in on or squeezes the target abnormality while applying a pressure of suitable proportion to the target abnormality such that consistent and uniform treatment to the target abnormality is formed.

A radiating section 54 that includes a loop 56 that is transitionable provides a user with the capability of treating target abnormalities with various configurations and/or dimensions, as described in greater detail below. Moreover, a radiating section 54 that includes a loop 56 that is transitionable provides a user with the capability of accessing areas of a patient with limited space, e.g., the cannula only needs to be as big as the diameter of the microwave antenna and not as big as the diameter of the loop 56.

In an alternative embodiment, the radiating section 54 is not made from a shape memory alloy and includes a pre-formed loop configuration that is sufficient to fully surround a target abnormality. A radiating section 54 that is not made from a shape memory alloy and that includes a pre-formed loop configuration functions as described above with respect the radiating section 54 that is made from a shape memory alloy. In the instance where a microwave antenna 50 includes a radiating section 54 (made from either a shape memory alloy or other suitable material) that is pre-formed, the microwave antenna 50 is configured to be positionable within a cannula of suitable proportion, e.g., a cannula having a diameter at least as big as a diameter of the pre-formed loop.

In certain embodiments, a portion of the microwave antenna, e.g., radiating section 54, may be coated with a non-stick material, such as, for example, polytetrafluoroethylene, commonly referred to in the art and sold under the trademark TEFLON®.

The generator 20, the needle cannula and/or the microwave antenna may be in operable communication with one or more image guidance devices 60 (FIG. 1). In one particular embodiment, the image guidance devices are selected from the group consisting of an ultrasound device 62, an x-ray device 64, a fluoroscopy device 66, a cat scan device 68, a computer tomography (CT) device, and magnetic resonance imaging (MRI) device 70, or combination thereof. The image guidance devices and operative features associated therewith are commonly known in the art and as such will not be discussed in detail.

With reference to FIGS. 2A-2E, and initially with reference to FIG. 2A, an example operation of microwave ablation apparatus 10 is described. More particularly, the operative features of the microwave antenna 50 are described in terms of use with a method 100 for treating an aneurysm. Typically, an aneurysm develops when a lumen wall “L” of a parent blood vessel “V” weakens. In certain instances, the aneurysm may include a sac “S” and a neck region “N” extending from the lumen wall “L” of the vessel “V,” as shown in FIG. 2A. Initially, the distal tip 36 of the cannula 30 is percutaneously inserted into a patient and adjacent the aneurysm, see FIG. 6 at step 102. More particularly, the distal tip 36 is positioned adjacent the neck “N” of the aneurysm (FIG. 2B). Thereafter, the distal end 52 including the radiating section 54 of the microwave antenna 50 is inserted into the cannula 30, deployed from the distal tip 36 of the cannula 30 and positioned adjacent the neck “N” of the aneurysm, see FIG. 2B and FIG. 6 at step 104.

In the illustrated embodiment, the radiating section 54 is made from a shape memory alloy. In this instance, the radiating section 54, or portion thereof, is configured to wrap around and close on or squeeze the neck “N” when electrosurgical energy, e.g., microwave energy, is transmitted to the radiating section 54 (FIG. 2C). More particularly, when the microwave energy is transmitted to the radiating section 54, the radiating section 54 returns to the “cold forged” state forming loop 56 that wraps around and squeezes the neck “N” of the aneurysm, FIG. 6 at step 108. In accordance with the present disclosure, the diameter of loop 56 including the corresponding closure pressure provided therefrom is configured to electrocautery treat (e.g., coagulate, cauterize, etc.) the neck “N” of the aneurysm such that consistent and uniform treatment is formed at the neck “N”. As a result thereof, a mass is formed between a portion of the aneurysm and the lumen wall “L” defined by the patient vessel “V.” The mass essentially shuts down the neck “N” and/or an opening of the aneurysm “A” such that blood is prevented from flowing into the sac “S” of the aneurysm and is re-lined to the blood flow path, see FIG. 2D, for example. In certain instances, the aneurysm may be severed and, subsequently, removed from the body of the patient. Or, in some instances, the aneurysm may simply shrink to a size that poses no serious threat to the patient, see FIG. 2E.

In the instance where a radiating section 54 of the microwave antenna 50 is pre-formed, the radiating section 55 functions similarly to that of the radiating section 54 described above.

With reference to FIGS. 3A-3D, and initially with reference to FIG. 3A, an example operation of microwave ablation apparatus 10 is described in terms of a method 200 for treating a fistula “F.” In a human body, certain types of blood vessels (e.g., artery and vein) are arranged adjacent each other (FIG. 3A). In certain instances, a fistula “F” may develop between a lumen wall of a patient blood vessel “Va” (e.g., an artery) and a lumen wall of another patient vessel “Vv” (e.g., a vein), see FIG. 3B. In certain instances, the fistula “F” may include a neck region “N” extending from the lumen wall of the vessel “Va” to the lumen wall of the vessel “Vv,” as shown in FIG. 2A.

Initially, the distal tip 36 is percutaneously inserted into a patient and adjacent the fistula “F.” More particularly, the distal tip 36 is positioned adjacent the neck “N” of the fistula “F” (FIG. 3C). Thereafter, the distal end 52 including the radiating section 54 of the microwave antenna 50 is inserted into the cannula 30, deployed from the distal tip 36 of the cannula 30 and positioned adjacent the neck “N” of the fistula “F,” see FIG. 3C.

As described above, the radiating section 54 may be made from a shape memory alloy. In this instance, the radiating section 54, or portion thereof, is configured to wrap around the neck “N” when electrosurgical energy, e.g., microwave energy, may be transmitted to the radiating section 54 (FIG. 3C). More particularly, when the microwave energy is transmitted to the radiating section 54, the radiating section 54 returns to the “cold forged” state forming loop 56 that wraps around and squeezes the neck “N” of the fistula “F,” FIG. 3C. In accordance with the present disclosure, the diameter of loop 56 including the corresponding closure pressure provided therefrom is configured to treat the neck “N” of the fistula “F” such that a consistent and uniform blockage is formed at the neck “N”. As a result thereof, a mass is formed between a portion of the fistula “F” and the lumen wall defined by the vessels “Va” and “Vv.” The mass essentially shuts down the neck “N” (and/or openings associated therewith) such that blood is prevented from flowing from one blood vessel, e.g., blood vessel Va, through the neck “N” and to the other blood vessel, e.g., blood vessel Vv, and is re-lined to the blood flow path, see FIG. 3D, for example. In certain instances, the fistula “F” may be severed.

With reference to FIGS. 4A-4D, and initially with reference to FIG. 4A, an example operation of microwave ablation apparatus 10 is described in terms of a method 300 for treating varicose veins. More particularly, a vein “V” includes leaflet valves “v” that prevent blood from flowing backwards within the vein “V” (FIG. 4A). Typically, a varicose vein develops when the valve “v” extending across lumen wall “L” of the vein “V” weakens. More particularly, when vein “V” become varicose, the leaflets of the valve “v” no longer meet properly and the valve “v” does not close, which allows blood to flow backwards within the vein “V,” which, in turn, causes the vein to dilate (FIG. 4B).

Initially, the distal tip 36 is percutaneously inserted into a patient and adjacent the vein “V.” More particularly, the distal tip 36 is positioned adjacent the valve “v” of the vein “V.” Thereafter, the distal end 52 including the radiating section 54 of the microwave antenna 50 is inserted into the cannula 30, deployed from the distal tip 36 of the cannula 30 and positioned adjacent the valve “v” of the vein “V,” see FIG. 4C. As described above, the radiating section 54 may be made from a shape memory alloy. In this instance, the radiating section 54, or portion thereof, is configured to wrap around the vein “V” adjacent valve “v” when electrosurgical energy, e.g., microwave energy, is transmitted to the radiating section 54 (FIG. 4C). More particularly, when the microwave energy is transmitted to the radiating section 54, the radiating section 54 returns to the “cold forged” state forming loop 56 that wraps around and squeezes the vein “V” in the proximity of the valve “v” (FIG. 4C). In accordance with the present disclosure, the diameter of loop 56 including a corresponding closure pressure provided therefrom is configured to close off the valve “v” and/or the vein “V” such that a consistent and uniform blockage is formed at the valve “v” and/or vein “V.” As a result thereof, a mass is formed in the vein “V” at the valve “v.” The mass essentially shuts down the valve “v” and/or the vein “V” such that blood is prevented from flowing through the vein “V.” With the vein “V” blocked, i.e., inoperable, other veins in the proximate area can take over.

With reference to FIGS. 5A-5C, and initially with reference to FIG. 5A, an example operation of microwave ablation apparatus 10 is described in terms of a method 400 for treating a blood vessel “V.” Initially, the distal tip 36 is percutaneously inserted into a patient and adjacent the vein “V.” More particularly, the distal tip 36 is positioned adjacent the blood vessel “V.” Thereafter, the distal end 52 including the radiating section 54 of the microwave antenna 50 is inserted into the cannula 30, deployed from the distal tip 36 of the cannula 30 and positioned adjacent the blood vessel “V,” see FIG. 5B. As described above, the radiating section 54 may be made from a shape memory alloy. In this instance, when the microwave energy is transmitted to the radiating section 54, the radiating section 54 returns to the “cold forged” state forming loop 56 that wraps around and squeezes the blood vessel “V” (FIG. 5B). In accordance with the present disclosure, the diameter of loop 56 including a corresponding closure pressure provided therefrom is configured to seal the blood vessel “V” such that a consistent and uniform blockage “B” is formed at the blood vessel “V,” FIG. 5C. As a result thereof, a mass is formed at the blood vessel “V.” In this embodiment, a suitable closure pressure may be from about 3 kg/cm² to about 16 kg/cm².

From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. For example, one or more modules associated with the generator 200 may be configured to monitor one or more electrical parameters, e.g., impedance, power, current, voltage, etc., associated with the radiating section 54 of the microwave antenna 50 while the radiating section 54 is treating tissue at a target tissue site, e.g., at the target aneurysm. More particularly, one or more sensors may be operably disposed adjacent the aneurysm and in operative communication with the module(s) associated with the generator 200. In this instance, for example, the sensor(s) may provide data pertaining to impedance of the microwave antenna 50 (or operative component associated therewith, e.g., radiating section 54) or the aneurysm during treatment of the aneurysm. In this instance, the sensor(s) may be configured to trigger a control signal to the module(s) when predetermined threshold impedance that corresponds to a specific aneurysm type or size is reached and/or detected. When the module(s) detects a control signal, the module may send a command signal to the generator 200 such that the electrosurgical power output to the microwave antenna 50 may be adjusted accordingly.

While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 

1-13. (canceled)
 14. A microwave ablation apparatus, comprising: a cannula configured to be placed relative to tissue; a microwave antenna movably disposed within the cannula and adapted to connect to a source of microwave energy; and a radiating section disposed along a distal portion of the microwave antenna and configured to deploy from a distal end of the cannula and deliver microwave energy to tissue, the radiating section having a non-looped configuration and a looped configuration, the radiating section remaining in the non-looped configuration until microwave energy is delivered from the source of microwave energy to the radiating section, wherein delivery of microwave energy to the radiating section transitions the radiating section from the non-looped configuration to the looped configuration.
 15. An electrosurgical apparatus according to claim 14, wherein the cannula includes a distal tip configured to penetrate tissue.
 16. An electrosurgical apparatus according to claim 14, wherein at least one of the cannula or the microwave antenna is configured to communicate with an image guidance device selected from the group consisting of an ultrasound device, an x-ray device, a fluoroscopy device, a cat scan device, a computer tomography (CT) device, and a magnetic resonance imaging (MRI) device.
 17. An electrosurgical apparatus according to claim 14, wherein the radiating section is formed from a shape memory alloy.
 18. An electrosurgical apparatus according to claim 14, wherein the radiating section is configured to wrap around the tissue upon transition of the radiating section to the looped configuration.
 19. An electrosurgical apparatus according to claim 14, wherein the radiating section is configured to squeeze the tissue upon transition of the radiating section to the looped configuration.
 20. An electrosurgical apparatus according to claim 14, further comprising a connector operably coupled to a proximal portion of the cannula and configured to electrically couple at least one of the cannula or the microwave antenna to the source of microwave energy.
 21. An electrosurgical apparatus according to claim 14, wherein at least a portion of the microwave antenna is coated with a dielectric material.
 22. An electrosurgical apparatus according to claim 14, wherein the radiating section defines a loop diameter in a range of about 10 mm to about 20 mm when the radiating section is in the looped configuration.
 23. An electrosurgical apparatus according to claim 14, wherein at least a portion of the radiating section includes a cross-section area having a shape selected from the group consisting of a circular shape, a flat shape, and an oval shape.
 24. A microwave ablation apparatus, comprising: a microwave antenna adapted to connect to a source of microwave energy and configured to be deployed from a cannula relative to tissue; and a radiating section disposed along a distal portion of the microwave antenna and configured to deliver microwave energy to tissue, the radiating section having a first configuration and a second configuration different than the first configuration, the radiating section remaining in the first configuration until microwave energy is delivered from the source of microwave energy to the microwave antenna, wherein delivery of microwave energy to the microwave antenna transitions the radiating section from the first configuration to the second configuration such that the radiating section wraps around the tissue.
 25. An electrosurgical apparatus according to claim 24, wherein the radiating section is linear when in the first configuration.
 26. An electrosurgical apparatus according to claim 24, wherein the radiating section is looped when in the second configuration. 